Solar adoption continues to grow. The gear needed is still relatively large, though, requiring dedicated space on something like a rooftop. However, innovators around the world have been working on ways to avoid that problem. Some take the approach of building solar panels on existing flat surfaces and some are using entirely different materials.

Inventing a new solar technology that can compete commercially with today’s solar cells is difficult, given existing deployment methods. But a transparent photovoltaic (PV) cell would change the rules of the game. The idea of transparent solar panels is exciting because you could turn every window (or even phone screen) into an energy-generating surface. How cool would that be?!

Generating power from everyday surfaces

MIT researchers are making transparent solar cells that could turn everyday products such as windows and electronic devices into power generators. That too without altering how they look or function. How?

Their newly invented solar cells absorb only infrared and ultraviolet light. Visible light passes through the cells unimpeded, so our eyes don’t know they’re there. Using simple room-temperature methods, the researchers have deposited coatings of their solar cells on various materials and have used them to run electronic displays using ambient light. They estimate that using coated windows in a skyscraper could provide more than a quarter of the building’s energy needs without changing its look.  

A novel design

For those with even a vague knowledge of how solar panels work, the concept of a transparent solar panel might seem absurd. Solar panels absorb solar energy and convert it into electricity. How can a panel simultaneously absorb solar energy while allowing it to pass through?

The concept is simple: capture the invisible UV spectrum while letting the visible spectrum pass through.

This was at the core of the idea of inventors. Three years ago, a team in MIT’s Organic and Nanostructured Electronics Laboratory began to tackle the problem using a different approach. Richard Lunt, then an MIT postdoc and now an assistant professor at Michigan State University, proposed making a solar cell that would absorb all the energy from the sun except the part that allows us to see.

All light is made up of electromagnetic radiation spanning a spectrum of wavelengths, each containing energy that potentially can be harvested by a solar cell. But the human eye can detect only part of that spectrum—the so-called visible light. With the right materials and design, the light that we can detect would pass through the solar cell to our eyes; the rest would be absorbed by the solar cell—and we’d never miss it.

While it would be impossible for such panels to be as efficient as opaque panels, researchers argue that since transparent panels could replace existing windows, they could make up for the inefficiency with volume. It’s estimated that there are 5-7 billion square meters of windows in the United States, with 2.5 billion additional square meters of glass installed every year around the world.

So, what’s the status of the transparent solar industry? Are we close to it being real — or is it one of those future tech things that sound great in sci-fi but won’t happen in our lifetime?

To be honest, for now, transparent solar isn’t at the point where you can buy panels off the shelf, and residential applications may be years away. The technology is proven to work, but is only about half as efficient as traditional solar.

However, the researchers believe that this engineering problem should be solved in the coming years, and their solar cells should be guaranteed to have a commercially viable lifespan.

No one actually what the future holds. But one thing is clear the duo of Science and Solar Energy could potentially help humanity get to a truly sustainable and greener future faster.